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31
votes
1answer
882 views

Transferring a large amount of data in parallel calculations

This question is inspired by one of @whuber's answers Consider the following code: ...
31
votes
2answers
917 views

Variable naming changes everything

I am having a rather unusual problem I do not understand with Mathematica where renaming one of the variables of my function causes the function to stop "working". Here is the example of the code ...
28
votes
3answers
809 views

No warning when extrapolating with Plot

One of the most annoying "features" of Mathematica is that the Plot family does extrapolation on InterpolatingFunctions without ...
27
votes
2answers
699 views

DeleteDuplicates not deleting duplicates

It is not surprising that DeleteDuplicates[{5,5.}] returns {5,5.} because DeleteDuplicates ...
26
votes
6answers
1k views

ColorData[“VisibleSpectrum”] is wrong?

I am trying to visualize the visible spectrum using the built-in ColorData["VisibleSpectrum"] function which "colors based on light wavelength in nanometers". But I ...
25
votes
2answers
739 views

Strange ::usage behavior in v9

Note: This is fixed in 9.0.1. Something has gone wrong with usage in Mathematica 9. Would someone tell me how to fix it? I define a function ...
25
votes
0answers
579 views

What calendar is Mathematica using for dates in the distant past?

It appears that Mathematica treats all dates as proleptic Gregorian dates by default, a hypothesis that can be easily tested by using AbsoluteTime to compute the ...
24
votes
2answers
646 views

Template completion

In version 8, if one evaluates test::usage="test[x,y]"; then types test, then shift-cmd-k (or shift-ctrl-k), a template ...
23
votes
2answers
389 views

eigenvector bug?

This bug was fixed in version 10.0.0 I have a fairly simple $3\times3$ complex matrix, $$ M=\left( \begin{array}{ccc} \frac{7}{2}-\frac{i}{2} & -1+i & \frac{1}{2}+\frac{5 i}{2} \\ -1+i ...
22
votes
2answers
1k views

Debugging memory leaks

I've written my incredibly complex, incredibly elegant analysis function, that works great on small test data. But when I run it on my real (bigger) data set it keeps running out of memory. It turns ...
20
votes
4answers
781 views

An apparently “simple” limit?

Let $c$ and $h$ be real values. I was using Mathematica to compute the limit $(h \rightarrow \infty)$ of the following expression: $$ \frac{\left(h^2 +c^2 h^2 + \sqrt{4 h^2+\left(h^2+c^2 ...
20
votes
1answer
216 views

M9 performance regression for Fold?

I noticed an over 10x performance drop on Mathematica v9.0.1 (as Oleksandr R. commented, also v8) compared with v7.01 for this code: ...
19
votes
1answer
448 views

What is wrong with triangle PlotMarkers in v.10.0.0?

In Mathematica 10.0.0 we have built-in graphical triangle PlotMarkers. Let us look closer on them: ...
19
votes
2answers
264 views

Plotting a defined function gives different results from plotting the function directly

Consider the following piece of code: function[t_]:=Exp[-9 t^2]; LogLogPlot[{function[t],Exp[-9 t^2]},{t,.01,100}] I expect the two plots to exactly overlap each ...
18
votes
3answers
353 views

Error changing Dataset using Part

In the new guide Computation With Structured Datasets we can find this part, on how to change a Dataset But if we create a Dataset like: ...
18
votes
2answers
270 views

Negative probability?

I am trying to get the sum of the squares of seven random variables, all uniformly distributed. This is what I tried. ...
18
votes
1answer
285 views

Kernel inexplicably hangs if I define a pure function without suppressing output

Save any unsaved work before trying as it may crash Mathematica and other programs by filling up the memory! In v9.0.1.0 on OSX 10.8.5, if I start a new session and define two functions ...
17
votes
2answers
278 views

Graphics elements do not line up perfectly in exported PDFs

Graphics elements do not always line up perfectly in exported PDFs using "Save As..." method. Take, for example: ...
17
votes
3answers
462 views

Memory Leak in Frontend - anyone know a workaround?

When using Rasterize on a Graphics expression composed of many differently coloured Graphics objects memory is allocated in the frontend which is then not released or reused when a similar graphic ...
17
votes
1answer
178 views

BitShiftRight produces incorrect results in Version 10

With Mathematica 10 for Mac, BitShiftRight works properly on lists of up to 100000 numbers, but appears to give incorrect results when threaded over lists of 100001 ...
17
votes
1answer
389 views

Incorrect result from Integrate

I attempted to calculate the following integral: ...
17
votes
2answers
464 views

Have I found a bug in Integrate?

The following command gives 0 in Mathematica 9.0.1. ...
17
votes
1answer
294 views

Specifying non-conflicting PlotTheme options

I am trying out Mathematica 10 on https://programming.wolframcloud.com. $PlotTheme interested me a lot because it finally produces nice plots (probably) without the ...
17
votes
1answer
372 views

Kernel crash after idle in version 10.0

In version 10.0, when I leave the Mathematica section idle for some time (of order an hour), the kernel quit automatically. The syntax highlighting is gone and the variables that has defined before ...
16
votes
1answer
510 views

When importing GIF animation, how to find the correct list of “DisplayDurations”?

When importing GIF animations with variable frame durations, the settings for "DisplayDurations" are not recovered correctly. As an example, I'm using the movie from this earlier question: Here I'm ...
16
votes
1answer
388 views

How to fix broken InterpolatingFunction?

I have an InterpolatingFunction based on irregularly-gridded data, like this: ...
16
votes
2answers
761 views

How to compute the inverse CDF properly?

Note: this has been fixed in version 9. I want to compute the CDF and inverse CDF of the hyperbolic distribution: ...
16
votes
2answers
589 views

Exporting a dashed plot with a color gradient to a vector graphics format ruins the dashing

When exporting a dashed plot with a color gradient to a vector graphics format such as EPS or PDF, the dashing is partly ruined. For example, this command: ...
16
votes
1answer
236 views

Bug in RepeatedNull?

RepeatedNull appears to be buggy (versions 8.0, and 9.0). Define f as follows: ...
16
votes
1answer
672 views

Bug in Solve (Mathematica 9)

Just came across the strangest bug under both Mathematica 9.0.0 and 9.0.1. If one enters: Solve[m == p Sin[x] && -Pi/2 < x < Pi/2, x] ... then ...
15
votes
3answers
387 views

How can I set Grid alignments using numbers?

There is an example in the Alignment documentation (it also appears in the Grid documentation): ...
15
votes
1answer
769 views

How to export and import Graphs with additional data?

I'm trying to export and then later import graphs with additional data added such as VertexLabels and EdgeLabels. When I export ...
15
votes
2answers
852 views

Why does Mathematica give the wrong answer when integrating?

I integrate Integrate[Exp[I Cos[b - c]] Cos[b], {b, 0, 2 Pi}] Mathematica gives: 2 I Pi BesselJ[1, 1] Which is indepedent ...
15
votes
2answers
258 views

Upon PDF export, edgeless rectangles do not tile perfectly, and corners may be cut. Is this a bug?

Note: this problem is no longer present in version 10. Exporting the following as a PDF file ...
15
votes
1answer
332 views

Why does LogLinearPlot sample its argument outside the specified domain?

I experience a weird bug in the function LogLinearPlot. If the input is an interpolation function, such as the one created like this, ...
15
votes
2answers
455 views

Pattern issues weird warning

Take for example head[b_[PatternSequence[_, _]]] := 9 I know this example serves no purpose as is. It also happens in useful examples such as ...
15
votes
1answer
438 views

How to work with characters from CJK Unified Ideographs Extension B correctly?

Background: Recently I'm trying to deal with some Chinese characters which belongs to the CJK Unified Ideographs Extension B block. The motive comes from some further interest following a former ...
15
votes
1answer
371 views

Quiet doesn't work with FindRoot when using Brent method

The following has no solution: FindRoot[x == 1, {x, 0.25, 0, 0.5}] And Mathematica correctly warns us: FindRoot::reged: The point {0.5} is at the edge of the ...
14
votes
4answers
466 views

HoldForm doesn't hold form

In Mathematica version 10, HoldForm no longer produces the same results as in version 8 (edit: I only have versions 10 and 8 installed, so can't compare to version ...
14
votes
4answers
234 views

Unexpected dots from Line

I have noticed cases where Line produces dots in a graphics object when I think it shouldn't. The first of these is: ...
14
votes
1answer
284 views

Adding three integer sparse matrices is very slow. Adding only two is fast

Adding more than two sparse matrices in one step in Mathematica 9 is very slow (in fact I couldn't even wait for it to finish). Here's an example. Let's generate a large sparse matrix: ...
14
votes
1answer
337 views

Why do Arrowheads interfere with ImagePadding?

Bug still present in version 10 under Windows. In a recent posting, Belisarius solved a problem related to the display of arrows on the x and y axes by setting ...
14
votes
1answer
1k views

Version 9 Blue Screen or Self-Test Error on Windows 7 64-bit

Update There is now an official response from Wolfram Support on this issue. Having recently installed Mathematica version 9 64-bit on Windows 7, I keep running into Self-Test Errors evaluating ...
14
votes
1answer
230 views

Mathematica 9 cannot solve a difference equation that Mathematica 8 can

Consider RSolve[{a[n + 1] == 2 a[n] + n (1 + 2^n), a[1] == 1}, a[n], n] Mathematica 8 can solve this quickly, but Mathematica 9, even after being allowed to run ...
14
votes
0answers
145 views

How to format usage messages such that function templates are parsed correctly?

Is it possible to format usage messages (with italic arguments etc) such that Mathematica 9 still parses function templates correctly? For example, plain usage messages work when pressing ...
13
votes
4answers
675 views

Mathematica gives wrong result while Wolfram|Alpha is correct

Why does Mathematica and Wolfram|Alpha give different results based upon the same code? I know Wolfram|Alpha's 7.85 is correct.
13
votes
1answer
283 views

High memory use while exporting a BMP

Something mysterious is going on when exporting images. I'm using Mathematica 9.0.1 on Windows 7 (64 bit), and find that the memory use is excessive when exporting to a bmp. But it doesn't happen ...
13
votes
3answers
2k views

Mathematica script - passing command line arguments

When using Mathematica script #!/usr/local/bin/MathematicaScript -script Print[$ScriptCommandLine] and running it with some arguments: ...
13
votes
2answers
371 views

Problem importing URL with Greek characters

I'm considering buying a car. So I thought why not make a web-crawler in Mathematica to pile-up car data? Brilliant idea. Then I found this Greek website, gocar.gr, which just so happens to have all ...
13
votes
1answer
337 views

RandomVariate returns values outside the support of a PDF

Let $X$ be a random variable with pdf: dist = ProbabilityDistribution[1/(Abs[x]*Log[Abs[x]]^2), {x, -E^-2, E^-2}] Here are some pseudo-random drawings from it: ...